The present invention relates to a protective device for a non-contact feeder system which feeds power in a non-contact state to a moving body or the like which travels guided by a rail.
As a known non-contact feeder system, there is a system which assumes an occurrence of a fire and has a protective device to avoid such occurrence of the fire as disclosed in, for example, Japanese Patent Application Laid-Open No. 8-251704.
The above-described fire is assumed to occur when an eddy current flows through a metal (for example, a spanner) set in proximity to an induction line by means of magnetic flux generated from the induction line, through which a high-frequency current flows, to cause the metal to generate heat, and the induction line is heated by the heat and burned.
The protective device is composed of: an optical fiber cable laid along an induction line; a luminous unit and a light intercepting unit which are connected to the ends of this optical fiber cable; a detecting circuit connected to the light intercepting unit, for detecting a light damping factor, and outputting an alarm when the light damping factor exceeds a predetermined damping factor; and a circuit for shutting down the high-frequency current on the basis of the alarm output from this detecting circuit.
As a general protective device, there has often been used a conventional device in which a system always generating heat in a fed state is mounted with a bimetal which is actuated when this system abnormally generates heat so that the feeding to the system is shut down by the operation of the bimetal thereby to protect the system.
With the above-described known structure of the protective device of a non-contact feeder system, however, the following problems arise:
1. The above-described optical fiber cable has problems that when the cable is pressed or bent, the amount of transmittance thereby decreases, the detection distance thereof becomes shorter or the operation thereof becomes paralyzed, and that it is difficult to connect the cable and to execute work thereof.
2. Although the induction line is protected, no protection means are provided against abnormal heating of a pickup coil which occurs due to damage to the pickup coil placed on a moving body to oppose to the induction line, and against abnormal heating in the circuit substrate for feeding the power to a load by an electromotive force induced by the pickup coil.
3. In a system in which a bimetal is the only protection means, when the temperature of the system lowers due to a shut-down of the feeding, the bimetal becomes off again to resume the feeding, and the system is re-started while the cause for the abnormal heating is still unknown, which may possibly expand the abnormal state.
It is an object of the present invention to solve these problems, and to provide a non-contact feeder system which is not affected by bending, is easy to execute the work, and yet does not generate heat by a magnetic flux generated from the induction line, in addition to being capable of preventing a fire by detecting heat generated near the induction line.
In order to achieve this object, there is provided a protective device for a non-contact feeder system according to the present invention, in which an induction line for flowing a high-frequency current therethrough is laid along a moving path of a moving body, and the moving body is provided with a coil for inducing therein an electromotive force by a magnetic flux generated in said induction line so as to feed power to a load of said moving body by means of the electromotive force induced by said coil, characterized in that: a thermosensitive wire, formed by intertwisting a pair of conductors made of non-magnetic material and covered with insulators which soften at a predetermined temperature, is laid along the induction line; and when the ambient temperature exceeds said predetermined temperature, the insulators of the thermosensitive wire soften and the conductors are short-circuited, thereby causing the high-frequency current to be shut down.
With such structure, the insulators soften to short-circuit the conductors, whereby it is detected that there is a heating unit near the induction line. This detection output shuts down the high-frequency current, whereby the induction line is prevented from being heated, burning and causing a fire by the heat of the heating unit. Since it is formed by the conductors made of a non-magnetic material, the thermosensitive wire is not affected by the electromagnetic induction of the induction line, does not generate heat itself, is not affected by bending, and therefore is easy to execute the work.